Pipe structure and method of manufacture

ABSTRACT

A pipe section formed of a polymeric material which has a substantially constant thickness throughout, the terminal edge of the female connection having a reinforcement structure which rigidifies the end of the female connection and prevents deformation, the pipe section preferably having a flared end, and the reinforcement structure preferably being a semicircular channel formed at the end of the pipe section by a mandrel after initial extrusion of the pipe section; along with a method and apparatus for forming the pipe section, a pipe assembly including such pipe section, and a method of forming the pipe assembly.

FIELD OF THE INVENTION

[0001] This invention relates to pipes made from polymeric material, andmore particularly to pipes made as segments which are assembled intolarger pipe systems during installation.

BACKGROUND OF THE INVENTION

[0002] During recent years, it has become more and more common for pipesfor the transmission of fluids to be made from plastic materials.

[0003] Non-metal materials are made into various types of pipes byseveral methods. For instance, it is known to extrude PVC into variousshaped pipes. Another more economical method is the corrugated pipetechnique, which uses blow mold and vacuum mold techniques to produce apipe which is formed as extruded tubes of a polymer such as HDPE (highdensity polyethylene). Systems for fabricating such corrugated pipes aresold by Corma, Inc. of Concord, Ontario. A system of this type is alsodescribed in U.S. Pat. No. 5,296,188, which is herein incorporated byreference.

[0004] Polymer material pipes are generally manufactured as continuousextrusions which are then cut into sections. Frequently, each sectionhas a male end and a female end, and these sections are linkedsequentially across the distance needed for the pipe to extend. Thefemale end of the pipe, sometimes called a bell, receives the male end,sometimes called a spigot, of the next pipe therein.

[0005] One problem presented in such pipes derives from the fact that,during fabrication, the material from which the pipe is made is heated,and then cooled. As different portions of the pipe cool and shrink atdifferent rates, stresses are created. If the pipe is then exposed toheat, even such as that of strong sunlight, it may cause enough warmingto soften portions of the pipe.

[0006] The result of this is that portions of the bell are altered fromthe desired shape. As a result, the bell, which is optimally an openflared cone or skirt with a circular mouth, “flowers”, i.e., deformsinto a roughly clover-leaf or flower cross-section. This floweredstructure presents problems when the pipe sections are to be assembled,since the puckering of this shape may make the female end of the pipetoo small to easily accommodate the male end of the next pipe section.This means that the construction crew must try to pry the flowered bellapart to insert the male portion. This is inefficient in terms of laborcosts and time. Moreover, the flowering can render the pipe sectioncompletely unusable.

[0007] Similarly, stacking of the pipe section can create loads in thefemale end of the pipe section. If environmental factors such as heatcreated by sunlight or high ambient temperatures are present, this cansoften the material to the degree that deformation occurs.

OBJECTS AND SUMMARY OF THE INVENTION

[0008] It is therefore an object of the invention to provide a pipesection having a female end with a strengthened periphery.

[0009] It is also an object of the invention to provide a pipe sectionwith a female end resistant to deformation.

[0010] It is another object of the invention to provide a pipe sectionwhich is readily connected with another pipe section to form a pipeassembly.

[0011] It is still another object of the invention to provide a pipeassembly which is efficiently and cost-effectively fabricated in thefield and is reliably sealed against leakage.

[0012] It is a further object of the invention to provide a method andapparatus for making the pipe section of the invention.

[0013] It is yet another object of the invention to provide a method offabricating the pipe assembly of the invention.

[0014] Accordingly, in one aspect the invention is a pipe section whichcomprises a segment of polymeric material configured as a conduit havingan end strengthened by a reinforcing structure formed integrally of saidmaterial around the periphery of said end.

[0015] In another aspect, the invention is a pipe assembly foraccommodating fluid flow therethrough, which includes a first pipesection comprising a segment of polymeric material configured as aconduit and having a male end and a female end, said first pipesection's female end being flared and being strengthened by areinforcing structure formed integrally of said material around theperiphery of said female end, and a second pipe section comprising asegment of polymeric material configured as a conduit and having a maleend and a female end, said male end of said second pipe section being inthe female end of the first pipe section such that fluid may flow fromone of said sections into the other.

[0016] In a further aspect, the invention is a method of forming a pipesection, which comprises subjecting an end of a segment of polymericmaterial configured as a conduit to conditions sufficient to render thematerial proximate such end plastic, and turning the plastic polymericmaterial at such end back away from the end to form an integralreinforcing structure.

[0017] In yet another aspect, the invention is method of fabricating apipe assembly for accommodating fluid flow therethrough, said assemblyincluding a first pipe section comprising a segment of polymericmaterial configured as a conduit and having a male end and a female end,said female end being flared and being strengthened by a reinforcingstructure formed integrally of said material around the periphery ofsaid female end, and a second pipe section comprising a segment ofpolymeric material configured as a conduit and having a male end and afemale end, which method comprises bringing the female end of said firstpipe section and the male end of said second pipe section intoapproximate registration by inserting the male end of the second pipeinto the flared female end of the first pipe section, and connecting themale end of the second pipe section and the female end of the first pipesection when the two sections are in alignment, such that fluid may flowfrom one of said sections into the other.

[0018] In still another aspect, the invention is an apparatus forforming a reinforcing structure on an open end of a polymeric pipesection, which has a mandrel having a wall for contacting said pipesection. The mandrel includes a first portion wherein the wall isconfigured to be received in the open end of the pipe section, andanother portion in which the wall extends outwardly of the first portionin arcuate fashion such that an annular pocket is formed. The apparatushas means for holding the pipe section in an orientation such that itand the mandrel can be brought into contact, with the mandrel's firstportion being first received in the opening at the end of the pipesection. The apparatus also has means for causing movement of themandrel and the pipe section holding means relative to one another suchthat the mandrel and the pipe section come together with the mandrel'sfirst portion being received by the opening at the end of the pipesection, and thereafter the annular pocket of the third portion cominginto contact with and deforming the end of the pipe section to form areinforcing structure.

[0019] Of course, it will be understood that the invention pertains notonly to straight-line pipe sections but also to all otherconfigurations, such as elbow-shaped or T-shaped fittings.

[0020] Substantial benefits are conferred by practice of the invention.The provision of a reinforcing structure integral with the subject pipesection, proximate the periphery of the female end, effectivelystrengthens the structure so that it maintains its desired shape,resists deformation during storage before use, and can withstand roughhandling during connection of other piping to it. The pipe assemblyincorporating such pipe section is cost effectively fabricated in thefield and has increased strength at the point of interface during theconnection operation, with the result that such operation is made easierand more efficient. And, the method and apparatus for making the pipesection, as well as the method for making the aforementioned pipeassembly, of the invention are correspondingly convenient and costeffective.

[0021] Other objects and benefits of the invention will become apparentfrom the present specification, and the invention will be set forth inthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a partly cut away elevational view of a pipe section ofthe invention.

[0023]FIG. 2 is a partially cut away elevational view of the connectionbetween the male and female connection portions of two adjacent pipesections according to the invention.

[0024]FIG. 3 is a cross sectional view taken through the centerline ofthe female connection portion of a pipe section according to theinvention.

[0025]FIG. 4 shows an enlarged partial view of FIG. 3.

[0026] FIGS. 5 to 10 are enlarged views similar to that of FIG. 4,showing alternate embodiments of the invention herein.

[0027]FIG. 11 is a cross-sectional view of a pipe section of theinvention during manufacture.

[0028]FIG. 12 shows the initial fabricated female connection portion anda mandrel used to form it into the final desired structure of theinvention.

[0029]FIG. 13 shows an apparatus for forming the reinforced rimstructure in a pipe section.

[0030] FIGS. 14-16 are detailed sectional views of mandrels for formingrim structures of alternate embodiments.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS OF THE INVENTION

[0031] A central feature of our invention is formation of the integralreinforcing member on the female end of a subject pipe section. Thismember reinforces the female end's peripheral edge so that it canwithstand rough contact, jostling and the like when a male end ofanother pipe section is inserted and moved around to secure alignmentpursuant to connection of the pipe sections. Typically, practice of thepresent invention results in attainment of a hoop strength at thereinforced female end of at least 10, and preferably at least 15, pounds(e.g. for 4-inch diameter conduit) and in some cases 50, and preferablyat least 80, pounds (e.g., for 12-inch diameter conduit), hoop strengthbeing defined as the amount of force needed to laterally compress a pipeby 5% of its diameter. Moreover, the reinforcing member strengthens thefemale end of a subject pipe section, especially when flared, againstdeformation resulting from flowering by providing a skeletal frame whichholds the end in its desired shape. Also, the reinforcing memberprovides extra support while the pipe section is being stored, forexample, stacked in contact with other pipe sections. In the eventambient conditions such as heat, sunlight or the like cause a softeningof the pipe section's constituent material the reinforcing membercontributes added structural integrity so that degradation which mightotherwise occur can be prevented or at least decreased substantially.

[0032] While useful with a range of materials, the invention isespecially applicable to piping made of polymeric materials such aspolyethylene, polypropylene and PVC (in certain good embodiments,especially with polypropylene and PVC for instance, filler is alsoincorporated to reduce cost). Over and above such materials' intrinsicvalue in piping applications, they are particularly useful for producingpiping in a variety of shapes and styles, especially piping having acorrugated wall, which structure confers a relatively greater strengthto weight ratio vis-a-vis non-corrugated piping. This is a consequenceof the fact that the solidified polymeric materials of which conduit ismade characteristically are formed from precursors (such as thepolymeric material at elevated temperature, e.g., hot polyethylene, or areaction mixture subjected eventually to curing conditions) which haverheological properties permitting material flow until setting. Sincesuch precursors are highly formable, the polymeric materials areparticularly useful in extrusion processes, and other processes whichsimilarly require a high degree of formability, for making thecorrugated pipe sections on other shapes and styles contemplated inconnection with the present invention.

[0033] It follows that a preferred embodiment of the invention is amethod of forming a pipe section, which comprises subjecting an end of alength of polymeric material configured as a conduit with a corrugatedwall to conditions sufficient to render the material proximate said endplastic; shaping the plastic polymeric material proximate said end intoa flared portion; turning the plastic material at the end of said flaredportion back away from the end to form an integral reinforcingstructure.

[0034] The characteristics of the inventive pipe section as hereindescribed lead to a highly advantageous pipe assembly comprising atleast two pipe sections aligned and connected utilizing the invention.As brought out in more depth below, the present invention is veryeffective in maintaining the shape of a subject pipe section's femaleend so that a good fit between it and the male end of another pipesection can reliably be achieved, without the necessity for mechanicalworking of such female end in order to return it to its initialconfiguration conforming to and accommodating the shape of the male end.Moreover, when the female end of a subject pipe section is flared, thereinforcing member has the further effects of dimensionally stabilizingthe flared end (again for the purpose of reliably accommodating theother pipe section's male end), and strengthening the edge of the flaredportion so that movement therein of the other pipe section's end toachieve the desired alignment can be carried out with decreased dangerof deformation of the flared portion through rough contact, etc.

[0035] It can, therefore, be seen that another preferred embodiment ofthe invention is that it involves a method of fabricating a pipeassembly as aforesaid. In this method the pipe section is formed from apolymeric material, and it has a first tubular conduit. A femaleconnection on the end of the conduit has a generally cylindrical orconical structure which extends from the end of the conduit.

[0036] The terminal portion of the end structure is then heated to makethe material plastic. The terminal portion of the female connection anda mandrel are then pressed together. The mandrel has a pocket structurewhich causes the heated end of the female connection to bend backwardsto form a reinforcing rim structure. The heated end is then allowed toset. The cooled material of the rim structure reinforces the femaleconnection so that the flowering and other deformation problems of theprior art are not encountered.

[0037] To provide an integrated treatment of various structural aspectsof the invention, we consider a pipe assembly formed of at least firstand second pipe sections. The first pipe section comprises a tubularconduit with a female connection on the end. The second pipe section hasa tubular conduit with a male connection on its end. The femaleconnection receives the male connection so that the interior of thefirst pipe section communicates with the interior of the second pipesection, and water or other fluid can flow through the pipe assembly.

[0038] The female connection is formed of a polymeric material. It has afirst connection portion which is connected to the end of the conduitand extends longitudinally away from it. The female connection also hasan annular terminal edge which defines an opening at the end of the pipesection. The terminal edge has a reinforcement structure whichrigidifies the end of the female connection and prevents the floweringand other deformation problems of the prior art.

[0039] The reinforcement structure preferably includes a first annularportion formed integral with the first connection portion, a secondannular portion formed integral with this portion and extending radiallyinwardly or outwardly of the first annular portion, and a third annularportion which is formed integral with the second annular portion andextends longitudinally inwardly of the first pipe section.

[0040] In a preferred embodiment, the first pipe section has acorrugated outer structure of the same polymeric material as the femaleconnection affixed to the outer surface of the conduit. Preferably, thecorrugated outer surface is formed integral with the female connectionportion and is of material which is substantially the same thickness asin the female connection.

[0041] The female connection is also provided with a widening flaredopening to aid assembly of the pipes in, for instance, a trench, whereit is difficult to perfectly align the pipe sections for assembly. Thisis a valuable feature, since it is often fairly difficult to align thepipes precisely before pressing them together; provision of a flaredportion which helps guide another pipe section's end toward the femaleconnection site expedites attaining alignment. In such connection, itshould be noted that as used herein: the term “approximate registration”refers to the condition in which two pipe sections are orientedvis-a-vis one another that the male end of one can be or is insertedinto the flared female end of the other; and the term “alignment” refersto the condition of such section. The flare also enhances the structuralstrength of the end of the pipe section.

[0042] The rigidity of the female connection also may be enhanced by theuse of several crimped or creased portions of the end portion whichadditionally reinforce the structure of the female connection.

[0043] Now, with reference to the figures of drawing, as best seen inFIG. 1, a pipe section, generally indicated at 3, extends longitudinallybetween a male end or spigot, generally indicated at 5, and a female endor bell, generally indicated at 7.

[0044] Intermediate these two ends is a middle length of the pipesection generally indicated at 9, which is shown in contracted cut-awayin FIG. 1. The usual length of the pipe sections of this type is about20 feet, although there may be variations in this depending on theapplication and environment for which the use is desired. Innerdiameters of the pipes may vary widely, but in the preferred embodimentrange from about 10 inches to about 37 inches.

[0045] The pipe section 3 has an outer structure 11 which is preferablyformed of a continuous extrusion of polymer material, most preferably athermoplastic such as high density polyethylene (HDPE). The outerstructure 11 has a number of ring-shaped corrugations 13 each extendingaround the pipe. Alternatively, the outer structure may have a differentpattern, such as spiral corrugations.

[0046] The inside of the pipe section 3 is a tubular or cylindricalconduit 15 which extends between the male and female ends 5 and 7 andwhich is bonded to the corrugated structure 11 during fabrication of thepipe section. The conduit is preferably also formed as a continuousextrusion of polymer material, most preferably HDPE. This innercylindrical conduit 15 defines a passage generally indicated 17 goingthrough the pipe section from the male end 5 to the female end 7.

[0047] During assembly of the pipe sections, as best shown in FIG. 2,the male end 5 is inserted into the female connection 7. The femaleconnection provides a inwardly facing conical engagement surface 19against which abuts a resilient sealing member 21, which is a gasket,preferably an extruded rubber profile, supported in a radially outwardlyfacing recess on the last corrugation 23 of the male end 5 of the pipesection 3. Alternatively, a gasket may be held in the valley 24 betweenthe first and second corrugations at the male end 5, which gasket isradially wide enough to sealingly engage surface 19. This engagementbetween the sealing member 21 and the engagement surface 19 effectivelyseals the joint so that fluids passing through the pipe sections do notleak out in appreciable amounts. The engagement surface 19 flaresoutwardly at an angle of 1° to 10°, and most preferably about 5°, to thecenterline axis of cylindrical conduit 15.

[0048]FIG. 3 shows an enlarged cross-section of the female connection 7.It will be understood that the cross section of the pipe section will bethe same for all cross-sections through the centerline of the pipebecause the form of the preferred embodiment is a shape of rotation withcircular cross-sections. It will be understood that non-circularcross-section pipes, e.g., oval cross-sections, may also benefit fromthe present invention.

[0049] After the last corrugation 13, the female connection end 7comprises a bell structure 27 with an opening generally indicated at 25,into which the male end 5 can be inserted. The bell structure 27comprises a generally conical flare portion 29 which taperslongitudinally outward and radially outward from the end 31 of thecylindrical conduit 15. This taper extends to the wall portion 33 whichprovides the inwardly facing engagement surface 19 against which thesealing member 21 of the male end 5 engages. Wall portion 33 tapersoutward at an angle of about 1° to 10°, and most preferably about 5°, asindicated above.

[0050] Longitudinally outward of engagement surface 19, the wall portion33 includes a further flared second flare section 35. This flare section35 flares outward at a flare of about 15° to 30°, and most preferablyabout 20° from the centerline of the conduit 15 and preferably has alongitudinal length of about 1 to 2 inches, and most preferably 1.5inches.

[0051] To rigidify the end opening 25 of female connection 7, the flareportion 35 is also provided with a plurality of small corrugations orcrimps 37 which provide a ribbed annular portion which extends aroundthe circumference of the conical flare section 35. In the preferredembodiment there are three crimps 37, but it will be understood thatdepending on the thickness of wall used and the length of this flaresection 35, more or fewer crimps may be used.

[0052] Flare portion 35 is flared out at an angle of about 20°, whichallows for insertion of the male end 5 into the female connection 7 withsome degree of angular play. In common installation of such pipesections, a trench is dug and the pipe section of 20 feet in length islowered by the use of machinery such as a back hoe. As the pipe islowered into the trench it may be fairly difficult to ensure that theaxis of the second pipe section aligns with the axis of the first pipesection perfectly. The angulation of flare portion 35 allows for someplay or tolerance in the alignment, in certain good embodiments up to asmuch as 20 or even 30° as the male end 5 is settled into the femaleconnection 7.

[0053] The wall portion 33 extends to a longitudinal terminal endindicated at 39. This longitudinal terminal end 39 is provided with areinforcing rim structure which keeps the shape of the mouth 25 of thefemale connection 7 circular.

[0054] As best seen in FIG. 4, the reinforcing structure comprises afirst portion 41 formed integral with the distal end of the second flareportion 35. This first portion 41 extends longitudinally outward of thepipe section 3. Formed integral with the first section is a secondsection 43 which curves to extend radially outward from first portion41. The third portion 45 is formed integral with second portion 43 andthis extends backwards in a longitudinal direction towards thelongitudinal center of the pipe section 3, spaced from the first portion41. Third portion 45 has a terminal end portion 47 which is spaced fromthe first portion 41.

[0055] These annular structures combine to form an annular reinforcingstructure which is roughly a U-shaped channel.

[0056] The U-shaped channel has a curved cross-section taken through thecenterline of the pipe section. The radius of curvature of this channelis preferably about 1.25 times the thickness of the material of theflare portion, although the radius may be as large as 4 times thethickness of the material.

[0057] When the bell 7 is formed by extrusion it has a substantiallyuniform thickness throughout. The preferred thickness varies with thesize of the pipe. A 12-inch diameter pipe will preferably have athickness of about 0.110 to 0.112 inches. A 30-inch inside diameter pipewill preferably have thicker material, about 0.185 inches, and a 60-inchinside diameter pipe will preferably be of material about 0.25 inchesthick.

[0058] The combination of the reinforcing structure and the 20° flare isremarkably sturdy, structure, as much as about five times stronger thanthe same pipe without the flare or reinforcement. A deformation testcomparing two 12″ pipes, one with a flare and reinforced rim asdescribed herein, and the other identical, but with no rim or flare,yielded striking results. A 5% deformation of the unflared andunreinforced pipe required a compressive lateral load of 26 pounds. Toachieve the same 5% deformation in the reinforced and flared piperequired a load of 122.5 pounds.

[0059] The curving structure of this reinforcing ring formed by theportions 41, 43 and 45 also provides an additional benefit in that nocorners project either in a longitudinal direction or radially. Duringassembly of the female connection 7 with the male end 5, the roundnessof all corners prevents the end portion 39 from catching the resilientsealing member 21 and dislodging it from its position on the firstcorrugation 23 in the male portion 5 and also significantly reduces theinsertion force.

[0060]FIGS. 5 through 10 show alternate embodiments that can also beused to reinforce the end of the female connection 7. The same referencenumbers are used for similar parts in these embodiments.

[0061]FIG. 5 shows an alternate embodiment in which the third annularportion 45 is curved so that the terminal end 47 thereof contacts theouter side of flare portion 35. The result is that the reinforcingstructure defined by the three elements of portions 41, 43 and 45 is atubular structure reinforcing the rim of female connection portion 7.

[0062] In FIG. 6, a further alternate embodiment is shown wherein thethird portion 45 is pressed inward so that the third portion 45 liesadjacent to and engaging the first portion 41 on its radial outsidesurface.

[0063] Referring to FIG. 7, a further alternate embodiment is shownwherein the curvature of the reinforcing structure at the end of thefemale connection 7 does not have a curvature as pronounced as that inthe embodiment of FIG. 5. Instead of having the curvature ofapproximately a complete semicircle, the embodiment of FIG. 87 has across-section which is less than a semicircle and wherein the tangent tothe terminal end portion 47 of the third portion 45 is at an angle αfrom the perpendicular passing through the longitudinal axis of the pipesection. This angle α is preferably less than 90° and more than about10°, to produce some sort of channel structure in the rim. In theembodiment shown, the angle α is about 60°.

[0064] Referring to FIG. 8, an embodiment is shown wherein the thirdportion 45 of the reinforcing structure is connected to a furtheroutwardly disposed portion 49 which engages and overlies the radiallyouter surface of third portion 45 so as to provide a generally S-shapedreinforcing structure at the mouth of female connection 7.

[0065] A further alternate embodiment is disclosed in FIG. 9, wherein anannular bead 51 is formed around the outside of terminal end 53. Thisbead 51 is annular and reinforces outer rim 53 against deformation outof a desired shape in a fashion similar to the reinforcing structures ofFIGS. 4 through 8.

[0066] This bead 51 may be formed by reforming the end of the extrudedbell of female connection 7 without any additional material. Analternate possibility is that the bead 51, which is of the same materialas used for the extrusion, which is preferentially high densitypolyethylene, is additional material applied around the longitudinalterminal end 53 of the formed flare portion 35. The application of thisbead 51 is under conditions sufficient to cause it to fuse with thematerial of the flare portion 35 and structurally unite with thatmember. This bead may be applied as a string of polyethylene or othersuitable material wrapped around the flare portion 35, or as a loop ofpolyethylene material which is shrunk around the flare portion 35.

[0067] It will be understood that reinforcement structures such as thebead need not be at the terminal end of the female connection, but mayprovide beneficial structural reinforcement when spaced slightly inwardfrom the end, so long as the reinforcement is in the end region of thepipe to prevent deformation of the end.

[0068] It will also be understood that these embodiments are exemplaryof reinforcement structures, and that other cross-sectional structuresmay be readily devised by those of skill in the art.

[0069]FIG. 10 shows another alternative embodiment which can be appliednot only to the rim structure indicated in FIG. 4 but to the reinforcingrim structures of FIGS. 5 through 9, as well. As seen in FIG. 10, thecurvature of the reinforcing structure may be reversed so that itextends radially inwardly of the flared portion 35. In FIG. 10, thereinforcing structure consists of a first portion 53 extendinglongitudinally outwardly, a second portion 55 extending radiallyinwardly and a third portion 57 which extends back longitudinallytowards the longitudinal center of the pipe section 3. The inwardterminal end 59 of this inward reinforcement structure is spacedinwardly from the first portion 53.

[0070] The configuration of this reinforcing structure may be varied soit can have a cross-section similar to that of the embodiment of FIG. 6(a tube structure), FIG. 7 (a folded structure), FIG. 8 (a less thansemicircular arch), or FIG. 9 (an S-shaped, folded structure). It willalso be understood that the same concept can be applied to the structureof FIG. 10, wherein the bead 51 would be mounted on the radial inside ofthe lip 53 of the mouth of the female connection.

[0071] The preferred method of manufacture of the pipe sections of theinvention is by extrusion of polymer material. Particularly preferred isthe corrugated pipe extrusion method discussed in U.S. Pat. No.5,296,188, and/or embodied in the Corma, Inc., system sold under themodel designation “3020”.

[0072] Such a system produces a generally continuous corrugated tubewhich is cut into separate pipe sections.

[0073]FIG. 11 shows a segment of the continuous tube which is cut toform the male and female ends 5 and 7. The corrugated tube comprises twotubular parisons or sheets of extruded material, preferably of athermoplastic nature, such as HDPE, which parisons have a substantiallyconstant thickness over the length of the pipe. The outer parison 50comprises the bell 7, including crimps 37, and the pipe structure 11with the corrugations 13. The inner parison 60 is a generallycylindrical tube which constitutes the conduits 15 of the pipe sections3. Both parisons are of the same material and are bonded together atannular regions 62 during the extrusion process.

[0074] The first step of processing after extrusion is that the pipesections are cut to separate them from each other. This is done bycutting completely through the extrusion at plane A of FIG. 11.

[0075] The next step of processing involves cutting through each of theparisons 50 and 60 with a skiving tool, which is usually a router heldin place to cut through one of the extruded parisons while the pipesection is rotated. Two cuts are made, inner parison 60 being skived atplane B and outer parison 50 at plane C. This frees a portion, referredto as “top-hat” 64, which is recycled.

[0076] The resulting female end 7 has a cross-section as shown in FIG.12.

[0077] As an alternative to this arrangement which requires skiving outthe “top-hat” is that in the area of the bell the inner parison 60 maybe pressed outward to form a double-walled bell shape. Such a structurewould only require a single cut, to separate the pipe sections. Theinterior shape would be correct without further skiving needed.

[0078] At this point, the pipe wall portion 33 has a longitudinal end 61which extends generally along the line of the generally conical surface19 of wall 33. It is this end 61 that is formed into the rim structure.

[0079] In order to introduce the rim structure, the female connection 7and a mandrel 63 are pressed together so the mandrel enters into theopening 25 of the female connection 7.

[0080] As best seen in FIG. 12, the mandrel 63 comprises a central bodyportion 65 which is generally circular about the central axis of thepipe section 3. This may be solid, or it may be toroidal, with a hole inthe middle and a similar radially outward configuration. The centralportion 65 fits into the opening 25 at the end of the pipe section, andthis first portion of the mandrel has a generally cylindrical outer wall67. The cylindrical outer wall 67 blends into a flaring frustoconicalwall 69, which flares outwardly at approximately 20° to impart a flareto the end structure 61 of the female connection 7.

[0081] The frustoconical surface 69 extends flaringly outward to pocketstructure 71, which includes a curving surface 73 which curves from theouter end of the frustoconical section upwardly and then back in alongitudinal direction towards the end section of the pipe structure,forming an annular pocket or trough generally indicated at 75.

[0082] In this stage of fabrication, the thermoplastic material iseither heated by a secondary source or the mandrel itself may be heatedto soften this material and make it pliable to form the reinforcingstructure. The softened end of the pipe is then pressed into themandrel, by movement of either the pipe or the mandrel, or bothtogether.

[0083] The engagement of the pipe with the mandrel is at specifiedtemperature, pressure and duration. For a 12 inch inner diameter pipewith a 0.112 inch wall thickness, the end of the pipe is heated to about350° F., and the mandrel and pipe are pressed together with a force ofabout 400 pounds. The engagement is maintained for about 15 to 20seconds, which imparts the proper shape to the pipe. These parameters,it will be understood, vary with the size of pipe, and may be variedeven with the same size pipe.

[0084] An apparatus particularly preferred for finishing the female end7 of the pipe section 3 is shown in FIG. 13. The female end 7 of thepipe is held in a rotary station indicated at 77 between rollers 79 and81 that rotate the pipe 3 in place.

[0085] First, skiving device 83, which has two routing devices 85 and 87mounted on a moving carriage, moves laterally to place the skivingdevice in operative position at the end 7 of the pipe 3. As the pipe isrotated, the top-hat (not shown in FIG. 13) is cut out. The skivingdevice 83 is then retracted to the position shown in FIG. 13.

[0086] Mandrel device 89 then descends on vertical track 91 to line upwith the end 7 of pipe 3. Heating device 93, preferably a gas torch or aquartz radiant heater, is then activated to heat and soften the materialat the end of pipe 3. The mandrel 63 is supported on pneumatic cylinderstructure 95, which, when activated, presses the mandrel 63 intoengagement with the end 7 of the pipe 3, forming the reinforcementstructure on the pipe.

[0087] The mandrel 63 is then retracted and the mandrel device 89 movesup to its starting position shown in FIG. 13.

[0088] The pipe is then cooled and allowed to set. Cooling may beassisted with an air mister.

[0089] Other systems for pressing the engagement of the pipe end withthe mandrel can readily be assembled by one of ordinary skill in theart. For example, a yoke that grips the end of the pipe may be attachedto a pneumatic press with the mandrel thereon which, when activated,presses the mandrel against the end of the pipe.

[0090] Different mandrel designs can be used to obtain the rimstructures of alternate embodiments shown in FIGS. 5 to 10.

[0091] For example the embodiment of FIG. 8 is preferably obtained bythe mandrel arrangement as seen in FIG. 14. Mandrel 97 has a slopingconical surface 99 which terminates at an abutment surface 101. A spotheating element 105 applies heat to a middle third of the annular endportion 103 while the mandrel 97 and pipe 3 are being rotated relativethereto. As the end portion 103 is pushed against the abutment surface101, the softened middle portion folds to form the S-shapedreinforcement.

[0092] The radially inwardly disposed reinforcement structure shown inFIG. 10 is preferably formed by a mandrel 107 as seen in FIG. 9.

[0093]FIG. 16 shows a preferred embodiment for formation of a bead 51 asseen in FIG. 9. The mandrel 109 is rotated adjacent a rotating roller111, which co-acts therewith to shape the bead 51 at the end of pipe 3.

[0094] The terms used herein are intended to be terms of descriptionrather than limitation, as those knowledgeable in the art with thisspecification in hand will be able to make modifications therein withoutdeparting from the spirit of the invention.

What is claimed is:
 1. A pipe section which comprises a segment ofpolymeric material configured as a conduit having an end strengthened bya reinforcing structure formed integrally of said material around theperiphery of said end, said structure including a portion which extendsback away from said end.
 2. A pipe section as defined in claim 1 ,wherein the reinforcing structure is formed at said end by turning theconduit material back over on itself.
 3. A pipe section as defined inclaim 1 , wherein the hoop strength of said end is at least 10 pounds.4. A pipe section as defined in claim 3 , wherein the hoop strength ofsaid end is at least 15 pounds.
 5. A pipe section, which comprises asegment of polymeric material configured as a conduit with a corrugatedwall, said conduit having an end portion which is flared, and which isstrengthened by a reinforcing structure formed integrally of saidmaterial around the periphery of said end, said structure including aportion which extends back away from said end.
 6. The pipe assembly ofclaim 5 , wherein the flared portion flares at an angle of about 15° to30° relative to the longitudinal axis of the conduit.
 7. The pipeassembly of claim 6 , wherein the angle is about 20°.
 8. The pipeassembly of claim 5 , wherein the flared portion includes at least onerigidifying crease structure, said crease structure being annular andextending substantially around the flared portion.
 9. A pipe sectioncomprising: inner and outer longitudinally extending generally tubularparisons each of high density polyethylene material and formed byextrusion, each parison having a respective substantially constantthickness throughout; the inner parison comprising a substantiallycylindrical longitudinally extending conduit having a passage thereinfor fluids to pass through the pipe section, said conduit having twolongitudinal ends and an outer surface; said outer parison comprising acorrugated structure surrounding the conduit and affixed to the outersurface thereof and a bell structure formed integral with the corrugatedstructure adjacent one of the ends of the conduit and projectinglongitudinally outward therefrom; said corrugated structure having amale connection structure secured adjacent the other end of the conduit,said bell structure forming a female connection structure configured tosealingly receive therein another male connection structure having aconfiguration substantially the same as said male connection of the pipesection; the bell structure comprising: a first flare section connectedwith the corrugated structure adjacent the associated end of the conduitand projecting longitudinally and radially outward therefrom, said flaresection including a radially inwardly disposed generally conicalengagement surface tapering outwardly at an angle of about 1 to 10° andconfigured to sealingly engage said other male connection structure whenplaced in the bell structure; a second flare portion formed integralwith and projecting radially and longitudinally outwardly from an outerend portion of the first flare portion and tapering outwardly at anangle of about 15 to 30° for a distance of about 1 to 2 inches; saidsecond flare portion including a longitudinal terminal end portion ofthe bell structure, said terminal end portion defining in the femaleconnection a generally circular end opening communicating with thepassage in the conduit; the terminal end portion including areinforcement structure comprising a first annular portion formedintegral with the second flare portion and extending longitudinallyoutwardly therefrom; a second annular portion formed integral with thefirst annular portion and extending radially outwardly therefrom; athird annular portion formed integral with the second annular portionand extending longitudinally inward therefrom; said reinforcingstructure being formed by shaping the terminal end portion to turn backon itself so that the reinforcing structure has a channel or tubularcross-section.
 10. A pipe assembly for accommodating fluid flowtherethrough, which includes a first pipe section comprising a length ofpolymeric material configured as a conduit and having a male end and afemale end, said first pipe section's female end being flared and beingstrengthened by a reinforcing structure formed integrally of saidmaterial around the periphery of said female end, said structureincluding a portion which extends back away from said end, and a secondpipe section comprising a length of polymeric material configured as aconduit and having a male end and a female end; said male end of saidsecond pipe section being in the female end of the first pipe sectionsuch that fluid may flow from one of said sections into the other.
 11. Apipe assembly comprising: first and second pipe sections; the first pipesection comprising a longitudinally extending tubular first conduitportion having a longitudinal end and a female connection portion onsaid end, said female connection portion having a first opening thereinand said conduit portion having a passage therein communicating with thefirst opening; the second pipe section comprising a longitudinallyextending tubular second conduit portion with a longitudinal end and amale connection portion on said end, said male connection having asecond opening therein and the second conduit portion having a passagetherein communicating with the second opening; said female connectionportion receiving the male connection portion therein so that thepassage in the first pipe section communicates with the passage in thesecond pipe section and so that fluid can move through the pipe assemblyby passing through said conduit portions and said connection portions;said female connection portion comprising a first connection portionconnected with the end of the conduit portion and extending in alongitudinal direction therefrom, said female connection portionincluding a longitudinal annular terminal end portion extending aroundsaid first opening and including a first annular portion formed integralwith the first connection portion and extending therefrom generallylongitudinally outwardly of the first pipe section; a second annularportion formed integral with the first annular portion and extendinggenerally radially inwardly or outwardly from the first annular portion;and a third annular portion formed integral with the second annularportion and extending longitudinally inwardly of the first pipe sectiontherefrom; said first, second and third annular portions togetherforming a generally circular reinforcement structure which strengthensthe terminal end portion to preserve a circular shape thereof.
 12. Thepipe assembly of claim 11 , wherein the first pipe section furthercomprises a corrugated outer structure, the first conduit portion havingan outer surface, said corrugated outer structure surrounding and beingaffixed to said outer surface.
 13. The pipe assembly of claim 12 ,wherein said corrugated outer structure is of the polymeric material,said corrugated outer structure being formed integral with said femaleconnection portion, the corrugated outer structure and the femaleconnection portion having a substantially uniform thickness.
 14. Thepipe assembly of claim 11 , wherein said first connection portionincludes a flare portion adjacent the terminal edge portion, said flareportion flaring radially outwardly and longitudinally outwardly of thefirst pipe section, thereby facilitating alignment of the first andsecond pipe section during assembly of the pipe assembly.
 15. The pipeassembly of claim 11 , wherein said second annular portion extendsradially inwardly from the first annular portion and supports the thirdannular portion radially inwardly of the first annular portion.
 16. Thepipe assembly of claim 11 , wherein said second annular portion extendsradially outwardly from the first annular portion and supports the thirdannular portion radially outwardly of the first annular portion.
 17. Thepipe assembly of claim 11 , wherein the third annular portion has aterminal end directed longitudinally inwardly of the first pipe section.18. The pipe assembly of claim 17 and said first connection portionproviding a radially inward facing engagement surface, and said maleconnection portion supporting thereon a gasket, said gasket engaging theengagement surface so as to substantially seal the connection betweenthe male and female connection portions to resist escape of fluid frominside said pipe assembly; and said first, second, and third annularportions being curvingly configured so that the terminal end portion ofthe female connection portion has no corners directed radially inwardlyand longitudinally outwardly of the first pipe section that couldcontact and dislodge the resilient seal member from the male connectionportion during assembly of the first and second pipe sections.
 19. Thepipe assembly of claim 11 , wherein said polymeric material is highdensity polyethylene.
 20. The pipe assembly of claim 12 , wherein thecorrugated outer structure and the first conduit portion are formedsimultaneously by extrusion of thermoplastic material.
 21. The pipeassembly of claim 11 , and said female connection portion being formedby extrusion of thermoplastic material.
 22. A pipe section comprising: alongitudinally extending tubular first conduit portion having alongitudinal end and a female connection portion on said end, saidfemale connection portion having a first opening therein and saidconduit portion having a passage therein communicating with the firstopening; the female connection portion being adapted to receive thereinin said opening a male connection of a second pipe section; said femaleconnection portion being formed as an extrusion of polyethylene materialhaving a substantially constant thickness throughout, said femaleconnection portion comprising a first connection portion connected withthe end of the conduit portion and extending generally in a longitudinaldirection therefrom, and an annular longitudinal terminal end portionextending around said first opening, said longitudinal terminal endportion including a generally annular reinforcement structure formedintegral with and around the terminal edge portion, which reinforcementstructure strengthens the terminal end portion to preserve the shapethereof and of the first opening.
 23. The pipe section of claim 22 ,wherein the first pipe section further comprises a corrugated outerstructure, the first conduit portion having an outer surface, saidcorrugated outer structure surrounding and being affixed to said outersurface.
 24. The pipe section of claim 23 , wherein said corrugatedouter structure is extruded of polyethylene material, said corrugatedouter structure being formed integral with said female connectionportion.
 25. The pipe section of claim 22 , wherein said firstconnection portion includes an angulated flare portion supporting theterminal edge portion, said flare portion flaring radially outwardly andlongitudinally outwardly of the first pipe section adjacent the terminaledge portion.
 26. The pipe section of claim 25 , wherein the flareportion flares at an angle of about 15° to 30° relative to the axis ofthe first conduit portion.
 27. The pipe section of claim 26 , whereinthe flare portion flares at an angle of about 20° relative to the axisof the first conduit portion.
 28. The pipe section of claim 25 , whereinthe flare portion includes at least one rigidifying crease structure,said crease structure being annular and extending substantially aroundthe flare portion.
 29. The pipe section of claim 25 , wherein saidreinforcement structure extends radially inwardly from the terminal endportion.
 30. The pipe section of claim 25 , wherein said reinforcementstructure extends radially outwardly from the terminal end portion. 31.The pipe assembly of claim 21 and said first connection portionproviding a radially inward facing engagement surface adapted to engagea resilient sealing member supported on said male connection portion soas to substantially seal the connection between the male and femaleconnection portions to resist escape of fluid from inside said pipeassembly and resist flow of external fluids into the pipe assembly; andsaid reinforcement structure being curvingly configured so that theterminal end portion of the female connection portion has no cornersdirected radially inwardly and longitudinally outwardly of the firstpipe section that could contact and dislodge the resilient seal memberfrom the male connection portion during assembly of the first and secondpipe sections.
 32. The pipe assembly of claim 21 , wherein thereinforcement structure has a cross section taken through the axis ofthe conduit portion which cross-section is a channel shape.
 33. The pipeassembly of claim 21 , wherein the reinforcement structure has a crosssection taken through the axis of the conduit portion whichcross-section is a U-shape.
 34. The pipe assembly of claim 21 , whereinthe reinforcement structure has a cross section taken through the axisof the conduit portion which cross-section is an arcuate shape ofbetween 100° and 180°.
 35. The pipe assembly of claim 21 , wherein thereinforcement structure has a cross section taken through the axis ofthe conduit portion which cross-section is a tubular configuration. 36.The pipe assembly of claim 21 , wherein the reinforcement structure hasa cross section taken through the axis of the conduit portion whichcross-section is an S-shape.
 37. The pipe assembly of claim 21 , whereinthe reinforcement structure has a cross section taken through the axisof the conduit portion which cross-section is that of a substantiallysolid bead of material.
 38. A pipe assembly comprising: a first pipesection; the first pipe section comprising a longitudinally extendingtubular first conduit portion having a longitudinal end and a femaleconnection portion on said end, said female connection portion having afirst opening therein and said conduit portion having a passage thereincommunicating with the first opening; the female connection portionbeing adapted to receive therein in said opening a male connection of asecond pipe section; said female connection portion comprising a firstconnection portion connected with the end of the conduit portion andextending generally in a longitudinal direction therefrom, and a flareportion extending from the first connection portion and being angulatedwith respect thereto so that said flare portion tapers radially andlongitudinally outwardly of the first connection portion; said flareportion including an annular longitudinal terminal end portion distal tothe conduit portion and extending around said first opening; saidlongitudinal terminal end portion including a generally annularreinforcement structure formed integral therewith, which reinforcementstructure strengthens the terminal end portion to preserve the shapethereof and of the first opening.
 39. The pipe assembly of claim 38 ,wherein the first pipe section further comprises a corrugated outerstructure, the first conduit portion having an outer surface, saidcorrugated outer structure surrounding and being affixed to said outersurface.
 40. The pipe assembly of claim 39 , wherein said corrugatedouter structure and the female connection portion are extruded ofpolyethylene material, said corrugated outer structure being formedintegral with said female connection portion.
 41. The pipe assembly ofclaim 38 , wherein the flare portion flares at an angle of about 15° to30° relative to the axis of the first conduit portion.
 42. The pipeassembly of claim 41 , wherein the flare portion flares at an angle ofabout 20° relative to the axis of the first conduit portion.
 43. Thepipe assembly of claim 38 , wherein the flare portion includes at leastone rigidifying crease structure, said crease structure being annularand extending substantially around the flared portion.
 44. The pipeassembly of claim 38 , wherein said reinforcement structure extendsradially inwardly from the terminal end portion.
 45. The pipe assemblyof claim 38 , wherein said reinforcement structure extends radiallyoutwardly from the terminal end portion.
 46. The pipe assembly of claim38 , and said first connection portion providing a radially inwardfacing engagement surface adapted to engage a resilient sealing membersupported on said male connection portion so as to substantially sealthe connection between the male and female connection portions to resistescape of fluid from inside said pipe assembly; and said reinforcementstructure being curvingly configured so that the terminal end portion ofthe female connection portion has no corners directed radially inwardlyand longitudinally outwardly of the first pipe section that couldcontact and dislodge the resilient seal member from the male connectionportion during assembly of the first and second pipe sections.
 47. Thepipe assembly of claim 38 , wherein the reinforcement structure has across section taken through the axis of the conduit portion whichcross-section is a channel shape.
 48. The pipe assembly of claim 38 ,wherein the reinforcement structure has a cross section taken throughthe axis of the conduit portion which cross-section is a U-shape. 49.The pipe assembly of claim 38 , wherein the reinforcement structure hasa cross section taken through the axis of the conduit portion whichcross-section is an arcuate shape of between about 100° and 180°. 50.The pipe assembly of claim 38 , wherein the reinforcement structure hasa cross section taken through the axis of the conduit portion whichcross-section is a tubular configuration.
 51. The pipe assembly of claim38 , wherein the reinforcement structure has a cross section takenthrough the axis of the conduit portion which cross-section is anS-shape.
 52. The pipe assembly of claim 38 , wherein the reinforcementstructure has a cross section taken through the axis of the conduitportion which cross-section is that of a substantially solid bead ofmaterial.
 53. A method of forming a pipe section, which comprisessubjecting an end of a segment of polymeric material configured as aconduit to conditions sufficient to render the material proximate suchend plastic; turning the plastic polymeric material at such end backaway from the end to form an integral reinforcing structure.
 54. Amethod of forming a pipe section, which comprises subjecting an end of asegment of polymeric material configured as a conduit with a corrugatedwall to conditions sufficient to render the material proximate said endplastic; shaping the plastic polymeric material proximate said end intoa flared portion; turning the plastic material at the end of said flaredportion back away from the end to form an integral reinforcingstructure.
 55. A process for extruding a pipe section, said processcomprising: continuously extruding a corrugated pipe extrusion of apolyethylene material, said extrusion comprising inner and outerparisons, said inner parison being a continuous cylinder having aninterior passage and an outer surface, the outer parison having at leasttwo corrugated structures and a bell portion therebetween extrudedcontinuously, the corrugated structures each being affixed to the outersurface of the inner parison; circumferentially cutting both parisons ofsaid extrusion between said bell portion and one of the corrugatedstructures to produce a pipe segment having a single bell portion and asingle corrugated structure; circumferentially cutting said outerparison of the pipe segment in said bell portion and circumferentiallycutting said inner parison adjacent the corrugated structure so thatsaid bell portion has generally conical portion defining a concaveopening in the bell portion communicating with the interior of the innerparison; pressing said annular end portion in engagement with a mandrel,said mandrel engaging the end portion of the bell structure andre-shaping the conical portion to have a flare portion adjacent theannular end portion, said flare portion being generally conical andtapering outwardly at an angle of about 20° mm; said engaging with themandrel causing said annular end portion to turn back radially outwardof the flare portion and form a lip structure having a general channelshaped cross-section on the end of the bell portion; allowing thepolyethylene material to set so that said lip structure reinforces saidopening to retain a circular shape.
 56. The method of claim 55 andfurther comprising heating the terminal end portion of the bellstructure prior to engagement with the mandrel.
 57. The method of claim56 , and said mandrel being heated to heat the end of the bellstructure.
 58. A method of fabricating a pipe assembly, said methodcomprising: forming a female connection portion for a pipe section froma polymeric material by extrusion, said pipe section including a firsttubular conduit portion having an interior passage therein and alongitudinal end with an opening communicating with the passage; thefemale connection portion having a generally tubular end structurehaving a first connection portion for connection with the end of theconduit portion, said end structure having a longitudinal terminalportion distal from the first connection portion, said end structurehaving a substantially constant wall thickness; heating the longitudinalterminal portion of the end structure to become plastic; and pressingengagement between the longitudinal terminal portion and a mandrel, saidmandrel being configured so that engagement of the mandrel with the endstructure of the female connector portion causes the plastic terminalend portion of the female connector portion to form a reinforcingstructure therein; and causing the polymer material of the femaleconnector portion to set so that said reinforcing structure reinforcessaid female connector portion retaining its shape.
 59. The method ofclaim 55 and said end structure being formed conical and extendingflaringly outwardly from the first connection portion at an angle ofabout 1° to 10°.
 60. The method of claim 59 and said flare angle beingabout 5°.
 61. The method of claim 58 and said end structure being formedconical and extending flaringly outwardly from the first connectionportion at an angle of about 15° to 30°.
 62. The method of claim 61 andsaid angle being about 20°.
 63. The method of claim 58 , and saidmandrel having a central body portion which extends in a first directioninto said end structure and an annular pocket structure extending aroundsaid central body portion, said pocket structure having a first pocketportion projecting radially outwardly from the central body portion anda second pocket portion extending in said first direction and spacedradially outward of the central body portion, said first and secondpocket portions and the central body portion defining therebetween anannular recess around the central body portion; said terminal endportion being formed with reinforcing crease structures rigidifying theflared shape of the female connection portion.
 64. The method of claim63 and said central body portion of the mandrel having a conical orfrustoconical flaring surface adjacent the pocket structure, saidflaring surface tapering inwardly away from the pocket structure so thatsaid terminal end portion of the female connector portion is given anoutwardly flared shape adjacent said reinforcing structure.
 65. Themethod of claim 58 and said polymer material being a thermoplastic. 66.The method of claim 65 and said polymer material being high densitypolyethylene.
 67. The method of claim 58 and said heating of theterminal end portion being achieved by heating of the mandrel.
 68. Themethod of claim 58 and said heating of the terminal end portion beingperformed by a secondary heat source, and said mandrel being cooled tocause the setting of the material.
 69. A method of fabricating a pipeassembly for accommodating fluid flow therethrough, said assemblyincluding a first pipe section comprising a length of polymeric materialconfigured as a conduit and having a male end and a female end, saidfemale end being flared and being strengthened by a reinforcingstructure formed integrally of said material around. the periphery ofsaid female end, said structure including a portion which extends backaway from said end, and a second pipe section comprising a length ofpolymeric material configured as a conduit and having a male end and afemale end, which method comprises bringing the female end of said firstpipe section and the male end of said second pipe section intoapproximate registration by inserting the male end of the second pipeinto the reinforced flared female end of the first pipe section, andconnecting the male end of the second pipe section and the female end ofthe first pipe section when the two sections are in alignment, such thatfluid may flow from one of said sections into the other.
 70. A method offabricating a pipe assembly, said method comprising: forming a pipesection from a polymeric material by extrusion, said pipe sectionincluding a first generally cylindrical conduit portion having aninterior passage therein and longitudinal end with an openingcommunication with the passage, and a female connection portion on theend of the conduit portion, the female connection portion having agenerally cylindrical or conical end structure connected with andextending from the end of the conduit portion, said conical endstructure having a longitudinal terminal portion distal from the end ofthe conduit portion, said end structure having a substantially constantwall thickness; and applying an annular bead of polymer material to saidterminal end portion, said annular bead reinforcing said end portion tomaintain a circular shape.
 71. Apparatus for forming a reinforcingstructure on an open end of a polymeric pipe section, which comprises amandrel having a wall for contacting said pipe section, said mandrelincluding a first portion wherein said wall is configured to be receivedin the open end of the pipe section, and another portion in which saidwall extends outwardly of said first portion in arcuate fashion suchthat an annular pocket is formed; means for holding said pipe section inan orientation such that it and said mandrel can be brought intocontact, with the mandrel's first portion being that part of it firstreceived in the opening at the end of the pipe section; means forcausing movement of the mandrel and the pipe section holding meansrelative to one another such that the mandrel and the pipe section cometogether with the mandrel's first portion being received by the openingat the end of the pipe section and thereafter the annular pocket of thethird portion coming into contact with and deforming the end of the pipesection to form a reinforcing structure.
 72. Apparatus as defined inclaim 71 , wherein said mandrel includes a second portion intermediatesaid first portion and said other portion, said second portion having awall which flares outwardly in respect of said first portion such thatwhen the second portion is brought into contact with the pipe section apart of said pipe section proximate the end is caused to flareoutwardly.
 73. The pipe assembly as defined in claim 31 , wherein saidconnection resists flow of external fluids into the pipe assembly.